Crankcase ventilation



' April 30, 1940. G. F. RODDEWIG CRANKGASE VENTILATION Filed Dec. 2'7, 1938 4, a 5 5 w 7 a AV 5 f V. I 4/ 6 8 m o i 2 2 \1 4 Q. Q I x4, I 3 w Gttornegs Patented Apr. 30,1940 V Y UNITED STATES PATENT OFFICE casivxcasa VENTILATION Gilbert F. Roddewig, Pontiac, Mich., assignor to Yellow Truck & Coach Manufacturing Company, Pontiac, Mich., a corporation of Maine Application December 27, 1938, Serial No. 247,822 4 Claims. (Cl. 123-119) This invention has to do with internal comthe depression in the manifold is increased above bustion engines of the type in which the cranknormal by rapid deceleration as described, case serves as a lubricant reservoir. thereby admitting air, vapors and gases from It is well-known that it is desirable to com the crankcase, diluting the mixture going to the tinually pass a stream of air through the crankcylinders and insuring substantially complete. It case during operation of the engine to remove combustion. To provide for ventilation of the diluents such as water and other combustion crankcase under normal operating conditions I products as well as unburnt fuel, which leak have provided a by-pass which preferably takes past the piston rings. The amount of dilution .the form of a small opening drilled through the In is increased when the engine is operating under valve permitting flow of a small stream of air I conditions unfavorable for combustion and this through the crankcase into the manifold under is especially the case when the car is rapidly all conditions. decelerated and the engine operates as a brake. The new system is very simple and inexpen- At such times the driver's foot is off the' throttle sive and may be readily installed on existing and the throttle is practically closed so thatthe engines. Further details of the invention are 15 supply of fuel mixture is greatly cut down but disclosed in the following specification.

the engine speed in the early stages of decelera- In the drawing:

tion remains high so thevacuum in the mani- Figure 1 is a side elevation of an internal fold is considerably above normal, A fairly combustion engine 'provided with my improved rich mixture is usually provided under such ventilating system. 20

conditions to prevent. stalling of the engine. Figure 2 is a vertical section through the Where the engine is operated for considerable engine on line 2-2 of Figure 1. periods under such conditions, as in the case of Figure 3 is a section on line 3-3 of Figure 1. city bus service, the oil in the crankcase is Figure 4 is a, section on line 4--4 of Figure 3. 5 rapidly diluted and some of the diluents ac- It) indicates an internal combustionerigine 1 cumulate in the form of a thick sludge in the having crankcase l2 and cylinders I4 supplied crankcase which interferes with lubrication and with combustible mixture from carburetor l6 makes it necessary to clean the crankcase at freethrough intake manifold IS. The supplytof mixquent intervals. The resulting poor lubrication ture to the manifold is controlled by the usual also causes a substantial increase in enginewear throttle valve 20 operated by the driver. The 30 especially on cylinder walls and pistons; crankcase l2 is provided with air inlet 22 which I have succeeded in devising a very simple may be equipped with air cleaner 24 as shown system of crankcase. ventilation which over- Air admitted to the crankcase through the inlet 4 comes all of the above disadvantages and makes 22 traverses the crankcase and passes upwardly 5 it possible to operate engines under the most alcngthe valve push rods through passages insevere conditions without objectionable dilution dicatedjat 26, into the overhead valve chamber of the lubricating oil and without accumulation I 28, and from there past ventilator control valve ofsludge in the crankcase. Engines equipped 30 through conduits 32 into the ends of the with my system have been taken down andexintake manifold, as shown in Figure 1.

amined after as much as twenty thousand miles The ventilator control valve 30 ishoused in a 40 of severe service in which frequent stops have casing 34 provided with a valve seat 36 towhich been made and the crankcases have been found the valve is yieldingly pressed by spring '38, the to be clean and free from sludge and the c mother end of whichbears against collar 40 carbustion chambers have been found to be clean ried by adjusting screw 42 threaded in closure and substantially free from accumulations of 44 of valvehou'sing 34. The adjusting screw 42 45 the by-products of combustion. Furthermore, is bored out to provide a guide in which the stem the oil has been found to be free from serious of ventilator control valve 30 is slidable. It will deterioration by dilution. be apparent that by adjusting the screw 42 the According to my invention the crankcase is spring 38 may be adjusted to exert the desired provided with the usual air inlet, preferably prodegree of seating pressure on the valve Ill. Con- 50 vided with an air cleaner in accordance with duits 32 are secured in any suitable manner to the usual practice, and with an air outlet conthe housing 34 beyond the valve 30 and its seat nected by a suitable conduit to the engine intake 36 and are connected in any suitable manner to manifold. In the conduit is provided a springthe intake manifold beyond the throttle valve 5 closed valve adjusted so that it will open when 20. Obviously, in someinstallations one conduit 32 may be suflicient. With the engine illustrated the two conduits connected to the ends of the manifold as shown have proven preferable because in this way ventilation is obtained with a minimum interference with the distribution of gaseous'mixture from the manifold to the cylinders.

It is important to note the aperture 46 drilled I in the head of ventilator control valve 30. In "the case of the bus engine, here illustrated, the

opening is about one-eighth of an inch in diameter.

The arrangement operates as follows: During normal operation of the engine, ventilator control valve 30 is closed but the hole It serves as a by-pass to permit a small amount of air to flow through the crankcase into the intake manifold. A flow of from 1 to 2 cubic feet per minute has been foundto be sufllcient in this particular engine to take care of gases blowing by the piston without interfering with idling of. the engine.

To insure against any such interferences under all conditions it will usually be found desirable to adjust the closed position. of

the throttle valve 20'to give sumcient mixture to insure a somewhat higher idling speed.

The ventilator control valve 30 remains closed under all ordinary operating conditions except when the driver takes his foot 011 the throttle and the engine operates as a brake to help bring the car to a stop. The amount of depression in 'the manifold is then high compared with that obtained under normal idling or running conditions and the tension of spring 30 isso adjusted that when this degree of depression exists in'the With this arrangement it has been foundthat after many thousands of miles of operation practicallyno sludge has accumulated in the crankcase even in the case of city busses which are subject to very frequent stops. Flu'thermore, owing to more complete combustion there is less accumulation of combustion products in the combustion chamber. The condition of the lubricating oil is also much improved since it is maintained substantially free of diluents as well as sludge so that the wear of the engine parts is much less because of better lubrication. This reduction in wear especially on the cylinder walls is quite appreciable and results in material in-.

valve in said outlet opening in the direction of air flow to the intake, means for yieldingly holding the valve on its seat, said means being so adjusted that the valve is closed under ordinary operating conditions and opens only when subjected to abnormally high suction obtaining when the throttle is rapidly closed to eflect rapid deceleration.

2. In the combination as defined in. claim 1, said valve having an aperture therein permitting a slight flow of air past the valve into the intake at all times.

3. The combination of an internal combustion enginehaving a crankcase serving as a lubricant reservoir and an intake through which combustible mixture is supplied to the engine, a

- throttle valve controlling flow of the mixture into said intake, an air inlet for said crankcase, an

intake, mea'ns substantially closing said outlet under normal operating conditions, .and means for opening said closing means, said last-named means being eifective only when the intake suction is at the abnormally high value produced by 1 rapid closing of the throttle.

4. The combination of an internal combustion engine having a crankcase serving as a lubricant reservoir and an intake through which combustible mixture is supplied to the engine, a

30 air outlet for said crankcase discharging into the 1 throttle valve controlling flow of the mixture into said intake, an air inlet for said crankcase,

an air outlet for said crankcase discharging into the intake, means substantially closing said outlet under normal operating conditions, means for 

